In many languages, there is such thing as T-V distinction. Basically, it's when you use different pronouns in "formal" (or "polite") speech, and in informal speech.

Now, I do realize there is no such thing in English directly. However, there are phrases that
indicate the change between the formal and informal pronoun. For example, in Russian, a phrase "перейти на 'ты'" means literally "to start using 'ты'", where 'ты' is the informal pronoun. Variations of this also exist in other languages.

So my question is, what is the best way to translate such a phrase into English? In Poul Andersen's book "Tau Zero", I've found a phrase

“That’s the main reason I
called you. Remember, during training I urged you to come here for
part of your furlough.” By now they were using the intimate
pronoun.

While this seems a little awkward, it does the job well. Are there any other ways of saying it?

This is an excellent example of something that is close to non-translatable. It is a question of a specific grammar feature that just does not exists at all in English. Of course, formality does exist, so the concept can be explained, just not directly translated. The best that can be hoped for without a full explanation (that is in comparable set of words) is just to mention that they are somehow on more familiar terms. Mentioning an 'intimate pronoun' pulls you out of the story and into either inscrutability for those who don't know and into linguistics for those who do.
–
MitchJul 30 '12 at 12:33

Or, if you're from Northern England, one uses words like love, duckie, etc. There's also the very strange my lover, which I'm assured still exists as a form of address between friends in some parts of England.
–
TRiGJul 30 '12 at 18:01

French has tutoyer. There is no equivalent English word, and you just have to get round it by saying something like 'they were now on more intimate terms, and it showed in the familiar forms of address they used with each other.'

Depending on the intended audience of your book, you might want to actually use the foreign pronouns in the character's dialogue, if you think there's any chance that your reader will understand them. Sprinkle one or two here or there, or throw one in at the moment when the character switches and then a little note of explanation.

"I'm happy to have met toi," he said, switching to the more familiar toi instead of the more formal vous.

That's interesting, I haven't thought of it from such an angle.
–
SingerOfTheFallJul 30 '12 at 13:13

You can’t “meet toi”, because that’s the wrong form of the pronoun. It makes no sense. It’s like saying meet ∗thine instead of meet thee.
–
tchristJul 30 '12 at 16:00

@tchrist Of course it isn't grammatically correct French, since it's an English sentence. The point is to introduce the foreign word, not to introduce the whole language. I can't think of any form of the "tu" pronoun that would work better there.
–
Mr. Shiny and New 安宇Jul 31 '12 at 2:13

This kind of semi-translation would work well for a technical or legalistic book where exact words matter, but it's probably too stilted in this case.
–
DanJul 31 '12 at 2:17

Although foreign language study is common enough nowadays that people will probably figure out what is meant, I find the language used in Anderson's example quite jarring. There is simply no equivalent concept in English, so trying to use English to explain it, even abstractly, is going to sound weird no matter what you do.

In Anderson's example, I question whether it's even relevant to call out the grammar. One could just say they were 'on friendly terms' or 'like old friends' or something that conveys the intimacy without diving into the grammar.

Of course English used to have formal and informal pronouns: "thou" was informal and "you" was formal. But over time it came to be considered polite to use the formal in more and more contexts until the informal was lost.

In religious circles people sometimes use "thou" to refer to God because that's how he's addressed in the King James Bible. I once heard someone say that we should address God as "thou" to be more respectful, which is a little amusing because it's exactly the opposite of the intent of the King James translators. (Off the top of my head I don't know if the thou/you usage in King James reflects the Greek and Hebrew or if that was something interjected by the translators.)

Today we generally indicate formal address by using a salutation and last name, and informal by using a first name. Like "Mr Jones" versus "Bob". And of course there are all sorts of things we do differently in formal versus informal speech, like in formal speech we avoid use of contractions and slang terms.

Your example reminds me of another Poul Anderson story, I think it was called "Day of Burning", but anyway, the story where humans have their second contact with the Merseians. Anderson says that the humans learned the Merseian language on their first visit, but by the time of this second visit the language had changed a great deal creating difficulties in communication. And so when he wants to show that the humans are speaking in an out-dated version of the language, he has them use Shakespear/King James type speech, saying "whither thou goest" and that sort of thing. I think that effectively gives the idea of how they would have sounded to the natives.

Likewise, if I was writing a novel and wanted to convey to the reader the idea that the level of familiarity between two people had changed to the point where they were now using informal speech, I think I'd have them saying, "How do you do, Mr Jones" at the beginning and "Hi, Bob, what's up?" later. The reference to shifting to the informal pronoun works for me because I know what he's talking about, but I'm sure many readers would not understand. Well, Anderson tends to write for a more literate audience, perhaps he was counting on most of his readers understanding.

The singular familiar nominative thou originally went with the plural familiar (and sometimes singular formal) ye, not with you, which was an oblique form. The corresponding oblique form of thou is thee. You moved over into a nominative rôle later on down the line.
–
tchristJul 30 '12 at 15:55

Here's a quote from Curse of Chalion by Lois McMaster Bujold. Our heroes have just met someone whose native language is not their own:

Iselle controlled a visible twinge of alarm and inclined her head graciously. In passable court Roknari, albeit improperly in the grammatical mode of master to warrior rather than master to servant, she said, "Blessings of the Holy Ones be upon you this day, Umegat."

Umegat's eyes widened, and his bow deepened. He returned a "Blessings of the High Ones upon you too, m'hendi," in the purest accent of the Archipelago, in the polite grammatical form of slave to master.

Cazaril's brows rose. Umegat was no Chalionese half-breed after all, it seemed. Cazaril wondered by what convoluted life's chances he'd ended up here. Interest roused, he ventured, "You are a long way from home, Umegat," in the mode of servant to lesser servant.

A little smile turned the groom's lips. "You have an ear, m'hendi. That is rare, in Chalion."

"Lord dy Cazaril instructs me," Iselle supplied.

"Then you are well served, lady. But," turning to Cazaril, he shifted modes, now to that of slave to scholar, even more exquisitely polite than that of slave to master, "Chalion is my home now, Wisdom."

the use of first names vs surnames (whether you address somebody as "John" or "Mr Smith");

the use of formal vocatives such as "Sir"/"Madam"/"Ma'am" etc.

Now, the issue is of course complicated because which form of address is used-- both in English and in languages with a grammatical T/V distinction-- in a given circumstance is subject to the personal preferences of the people concerned in addition to social norms in the language/culture in question. So for there to be a near match between the switch from (say) first name to surname in English vs T to V form in a language with a T/V system is probably quite a rare coincidence.

However, inasmuch as it is a match, it's common in English to say e.g. "we're on first name terms".